Join me in a thought experiment. Go back to when you began training for your instrument rating. Do you remember wearing a view-limiting device (VLD) of some sort? A hood, Foggles, something that fit over your glasses or otherwise restricted your view so you could (theoretically) only see the instrument panel and not the outside world?
I’d like to raise some questions: what is a VLD exactly and are they truly necessary? And has anyone ever done any research to prove that VLDs are beneficial?
Presumably, a VLD fulfills the requirement that some training, especially recurrency, be done “solely by reference to instruments,” but the FAA doesn’t define either what a VLD is nor what is meant by “solely by reference to instruments.”
In the regulations for the instrument rating, the FAA requires 40 hours of “actual or simulated instrument time.” The FAA instrument rating airman certification standards refer to "skills associated with…[operations] solely by reference to instruments.” Even the FAA Instrument Flying Handbook doesn’t get more specific, saying only: “You may log instrument flight time during the time for which you control the aircraft solely by reference to instruments. This can be accomplished by wearing a view-limiting device, such as a hood, flying an approved flight-training device, or flying in actual IMC.”
In its discussion of credit for currency using an aviation training device, the FAA seems to come close to a definition: “When instrument time is logged in an aircraft, a pilot wears a view-limiting device to simulate instrument conditions and ensure that he or she is flying without utilizing outside visual references.”
In other words, a VLD should prevent the pilot from being able to see and perceive outside visual references.
Anyone who has flown with a VLD knows that they do not prevent pilots from seeing outside visual references. Helicopter IFR students especially know that, depending on the rotorcraft, they might be able to see the outside world through chin bubbles (windows near the floor). But even pilots wearing the most restrictive of hoods or glasses can see outside references, for example, when looking at a compass mounted on the glare shield or when looking at the edges of the instrument panel.
But here’s the fundamental question that I’m raising: are VLDs even necessary? The thought experiment is to imagine that you never had to wear a hood during instrument training. You have full access to all of the visual cues from the outside world along with your instruments and avionics. Do you think you would have been a worse IFR pilot if you had learned instrument flying without a VLD? Are pilots not so focused on the instruments and avionics while learning instrument flying that whether or not they’re wearing a VLD is moot?
There is only one real way to find out, and that would be to conduct a study with two groups of instrument rating students: one group would train in the traditional manner, wearing a VLD, while the other group would not use a VLD. Afterward, a series of flights in actual instrument meteorological conditions would have to be done, with the requisite safety pilots/instructors, followed by an evaluation of the quality of each group’s training. Obviously, this would be frightfully expensive and I doubt any organization would like to give it a try.
But the fact remains that VLDs really don’t give instrument students a proper experience of what it’s like to fly IFR. Anyone who has flown much real-world IFR knows that they always use information from a variety of sources; they aren’t just staring at the instrument panel but are gaining valuable information by looking outside, including looking for traffic. IFR conditions are not universally so bad that you can’t see outside the windshield—they range from (very occasionally) zero-zero to in and out of clouds to perfectly VFR weather.
IFR flight training with VLDs is hopelessly unrealistic, and that’s why new IFR pilots who have never been exposed to actual IFR conditions find it so intimidating the first time they fly in the clouds. They aren’t used to the experience of having all that information available from the outside world, having been confined to a tiny rectangle of the instrument panel for so many hours. I would suggest that IFR training could be done without VLDs and the result would be a smoother transition to real-world IFR flying and no degradation in IFR flying quality.
The reason for the requirement that pilots train with VLDs is probably lost in history, but I suspect it's based more on a feeling about what seems right rather than any kind of rigorous study. However, I'm open to being proven wrong.
Incidentally, because there is no formal definition of VLDs, some pilots claim that using a baseball cap suffices. I’m pretty sure most designated pilot examiners wouldn’t allow this during an instrument rating flight test, but wearing a cap does give the pilot access to valuable peripheral information from the outside world and it could be a simple solution to this question if the FAA would allow it.